1. Field of the Invention
This invention generally relates to the field of semiconductor processing and more particularly to tracking and addressing manufacturing issues in a semiconductor fabrication facility.
2. Description of the Related Art
Fabrication of an integrated circuit entails the sequencing of numerous processing operations. During the manufacture of an integrated circuit from a bare wafer, various layers of dielectric, polysilicon, and metal are deposited, doped, patterned, etched, and polished to form specific features of the circuit such as gates, interconnects, and contacts. The step in this manufacturing process must be performed with care, since successful completion of each step typically depends on meeting some strict requirements. For example, at some steps in a processing sequence, one or more processing tools are used to modify the wafer to produce the circuit features by exposing the wafer to chemical conditions that must be tightly controlled. The various reactant gasses and solutions must generally be introduced with their constituents in specified ranges of pressures and concentrations, and must be used in particular temperature ranges for controlled durations of time. The lithography steps that introduce patterns for various layers onto the wafer have strict tolerances on the mechanical positioning of the wafer and the optical elements of the lithography tools. The polishing steps typically have a combination of mechanical and chemical requirements for successful operation. Throughout the process, a high degree of cleanliness is required to prevent damage to the wafers, and in effect, a contamination-free environment is required in all steps of production.
Altogether, a semiconductor fabrication line has numerous criteria for the successful production of integrated circuits. When one or more of these criteria is not met, the adverse situation is often observed only by its resulting effects on the wafer. These effects may be apparent in sensitive test structures designed to indicate adverse events in the processing steps, and they may also appear as failed devices on the wafer. An important task in a typical fabrication facility is the recognition and correction of adverse events in the processing steps to prevent the waste of valuable raw materials and unfinished wafers. The adverse events include instances where the mechanical, chemical, thermal, or temporal criteria are not met in the various processing steps, situations where contaminants are inadvertently introduced to the process, and other undesired conditions. The adverse events can arise from equipment failures as well as from inappropriate actions on the part of facility personnel. A great deal of equipment and personnel time is dedicated to detecting and recording the processing errors and other adverse events, but unfortunately, the collected data are often not used as well as they can be.
One reason why diagnostic information is often not fully utilized is that in some cases a previous problem occurs again, but is not immediately recognized as something that has been previously addressed. Thus, time may be wasted xe2x80x9creinventing the wheelxe2x80x9d while the correct cause and solution to the problem might be immediately available if the problem were recognized as an old issue.
Another issue is that even when problems are detected at an early stage in the fabrication facility, they are occasionally overlooked until they have a significant impact on the fabrication yield. This oversight often occurs from the lack of delegated responsibility to address the detected problem.
A third problem in the control of errors and other adverse events in the manufacturing process is the sheer volume of information collected about them. Sorting through the copious quantities of test data from a fabrication facility is a daunting task, even with the aid of statistical-analysis software. Much of the test data gathered is of little or no relevance when taken one piece at a timexe2x80x94early recognition of fabrication problems often depends on noting correlated deviations measured at different points in the process. The large amount of gathered data can greatly reduce the practicality of finding such independent corroborating measurements.
These and other problems arise in semiconductor manufacturing facilities trying to address processing errors and other adverse events in their early stages, before the underlying problems run further out of tolerance and cause large amounts of waste that could have been prevented by timely corrective action.
Presented herein is a method for recording and addressing out of control (OOC) events in a semiconductor manufacturing line. The method includes steps of (a) opening OOC entries, including lot records and issue records, in an OOC database, and (b) working the OOC entries. Opening an OOC entry is performed in response to one or more OOC events in wafer lots being processed in the manufacturing line. If an OOC event is an isolated occurrence pertaining to one wafer lot, a lot record is opened for the OOC event. If, however, the OOC event indicates a trend of repeated defects or failures, then an issue record is opened for the OOC event. Each issue record may be linked to one or more related lot records. Opening an OOC entry in the OOC database preferably includes assigning and recording an xe2x80x9cownerxe2x80x9d responsible for overseeing measures for addressing the OOC entry.
Working the OOC entries comprises (i) opening activity records in the OOC database, each of which is associated with an OOC entry and includes one or more corrective measures for the associated OOC entry, (ii) receiving user input on corrective measures for addressing the OOC events, and (iii) recording the measures in the activity records. Each activity record preferably indicates the status of corrective measures recorded therein. The method preferably also includes steps of (c) closing OOC entries after working the OOC entries, and (d) reassigning OOC entries if ownership is transferred for the entries.
This disclosure also describes a system for recording and addressing OOC events in a manufacturing line. The system comprises: (a) a plurality of computer systems, including a plurality of entry terminals for entering information on OOC events, (b) an OOC database coupled to the plurality of computer systems, (c) an OOC interface executing on one or more of the entry terminals and coupled to the OOC database, and (d) an OOC tracking program executing on one or more of the computer systems and coupled to the OOC database and to the OOC interface.
The OOC database is configured to store OOC entries and activity records for addressing the OOC entries. The OOC interface is operable to receive new OOC information, to receive measures for addressing OOC events, and to display information from the lot and issue records. The OOC tracking program is operable to open and modify OOC entries, including lot and issue records, in the OOC database. The OOC tracking program is preferably also operable to close OOC entries after the completion of all measures for addressing OOC events in all the activity records linked to the OOC entries.
Each OOC entry preferably has an ownership field, and the tracking program is operable to specify an owner of the OOC entry in the ownership field and to reassign the OOC entry to a new owner.
The disclosure further presents a computer-readable storage medium having program instructions recorded therein for recording and addressing OOC events in a manufacturing line